When you download cacheable content from the Internet on an iPhone, iPad, or iPod touch that's connected to your Mac, a copy of the download is stored on your Mac. The next time that an iOS device that’s connected to your Mac tries to download the same content, it downloads directly from your Mac through USB. This is called “tethered caching.”

Check requirements for tethered caching

To use tethered caching, here's what you’ll need:

An iPhone, iPad, or iPod touch with iOS 10.3 or later

A Mac with macOS Sierra, and either iTunes 12.6 or later, or Xcode 8.3 or later

Type or paste this command in Terminal, then press Return to start the tethered caching service:

sudo tethered-caching

Connect an iOS device to your Mac through USB.

On the iOS device, download cacheable content, like a software update.* After the download completes, safely disconnect your device.

Repeat steps 7 and 8 for all devices. If you use a USB hub, you can download cacheable content on all your devices simultaneously. When you start the download, your devices get the data directly from your Mac with an Ethernet cable.

For more information about the tethered-caching(8) command, open Terminal on a Mac with macOS 10.12.4 or later. Then run the man tethered-caching command.

* Instead of manually starting the download in step 8, you could use a mobile device management (MDM) solution to install the cached software on your connected iOS devices. When iOS devices are connected to a Mac through USB, they share the network and receive MDM commands.